Materials, devices, and methods for resonant ambient thermal energy harvesting using thermal diodes

Abstract

The present disclosure is directed to materials, devices, and methods for resonant ambient thermal energy harvesting. Thermal energy can be harvested using thermoelectric resonators that capture and store ambient thermal fluctuations and convert the fluctuations to energy. The resonators can include non-linear heat transfer elements, such as thermal diodes, to enhance their performance. Incorporation of thermal diodes can allow for a dynamic rectification of temperature fluctuations into a single polarity temperature difference across a heat engine for power extraction, as compared to the dual polarity nature of the output voltage of linear thermal resonators, which typically necessitates electrical rectification to be routed to an entity for energy storage. In some embodiments, the thermal diode can be applied to transient energy harvesting to construct thermal diode bridges. Methods for constructing such devices, and using such devices, are also provided.

What is claimed is: 
     
       1. A method of harvesting energy, comprising:
 operating a thermal resonance device having at least two thermal diodes to:
 translate a spatial temperature difference between the at least two thermal diodes by a heat engine into electrical energy having a single polarity voltage output, 
 
 wherein the thermal resonance device operates to translate the spatial temperature difference that results from movement-induced temperature fluctuations in which the thermal resonance device is disposed, the movement-induced temperature fluctuations including atmospheric lapse rate with respect to altitude, sea depth, geographical location, or sensors built into everyday objects, and 
 wherein the spatial temperature difference results from ambient thermal fluctuations directly captured by the at least two thermal diodes. 
 
     
     
       2. The method of  claim 1 , wherein operating a thermal resonance device further comprises causing a heat flow to travel from a first thermal diode of the two thermal diodes, towards the heat engine disposed between the two thermal diodes, and from the energy conversion component towards a second thermal diode of the two thermal diodes. 
     
     
       3. The method of  claim 1 , wherein operating a thermal resonance device further comprises causing each of the two thermal diodes to reach steady state when the spatial temperature difference between the two thermal diodes is translated into electrical energy. 
     
     
       4. The method of  claim 1 , further comprising:
 causing at least a portion of the electrical energy that results from translating a spatial temperature difference between two thermal diodes into electrical energy having a single polarity voltage output to be stored. 
 
     
     
       5. The method of  claim 1 , further comprising:
 causing at least a portion of the power that results from translating a spatial temperature difference between two thermal diodes into electrical energy having a single polarity voltage output to be used to at least one of power one or more components of an object or system associated with the thermal resonance device. 
 
     
     
       6. The method of  claim 1 , further comprising:
 determining a performance factor of at least one thermal diode of the thermal resonance device; and 
 optimizing the amount of electrical energy that is outputted by the thermal resonance device in view of the determined performance factor. 
 
     
     
       7. The method of  claim 1 , further comprising optimizing the amount of electrical energy that is outputted by the thermal resonance device by adjusting at least one of a thermal rectification value of the thermal resonance device, a dimensionless parameter of frequency oscillations of the thermal resonance device, a dimensionless parameter related to an onset of thermal rectification of the thermal resonance device, or a ratio of a thermal resistance of a linear thermal mass of the thermal resonance device to a mean thermal resistance of one of the two thermal diodes. 
     
     
       8. The method of  claim 7 , wherein optimizing the amount of electrical energy that is outputted by the thermal resonance device further comprises adjusting either or both of the thermal rectification value of the thermal resonance device and the dimensionless parameter related to an onset of thermal rectification of the thermal resonance device, the dimensionless parameter related to an onset of thermal rectification of the thermal resonance device comprising a sharpness of a change in thermal conductivity for at least one of the two thermal diodes. 
     
     
       9. The method of  claim 1 , wherein the ambient thermal fluctuations occur due to one or more of diurnal temperature fluctuations or movement-induced temperature fluctuations that include one or more of altitude, sea depth, or atmospheric lapse rate. 
     
     
       10. The method of  claim 1 , wherein each of the at least two thermal diodes includes a junction between a phase-change material and a phase invariant material. 
     
     
       11. The method of  claim 1 , wherein each of the at least two thermal diodes are disposed on opposite ends of a first and a second thermal mass such that the at least two thermal diodes are disposed on external boundaries with the environment. 
     
     
       12. The method of  claim 1 , wherein translating the spatial temperature difference between the at least two thermal diodes further comprises directly capturing and transforming ubiquitous temperature fluctuations via thermal rectification across the heat engine. 
     
     
       13. A method of harvesting energy, comprising:
 operating a thermal resonance device having at least two thermal diodes to:
 translate a spatial temperature difference between the at least two thermal diodes into electrical energy having a single polarity voltage output, 
 
 wherein a dominant frequency associated with at least one of the at least two thermal diodes is tuned to a dominant frequency of temperature fluctuations during operation of at least one of the at least two thermal diodes to capture maximum amounts of temperature fluctuations to yield larger power outputs. 
 
     
     
       14. The method of  claim 13 , wherein the spatial temperature difference results from ambient thermal fluctuations captured by the at least two thermal diodes. 
     
     
       15. The method of  claim 13 , wherein translating the spatial temperature difference is performed by a heat engine. 
     
     
       16. The method of  claim 12 , wherein translating the spatial temperature difference bypasses electrical rectification. 
     
     
       17. The method of  claim 1 , wherein the thermal resonance device is disposed below ground when translating the spatial temperature difference. 
     
     
       18. The method of  claim 1 , wherein the electrical energy is generated on a substantially persistent basis such that the thermal resonator generates heating or cooling throughout any cycle of the day. 
     
     
       19. The method of  claim 13 , wherein tuning the at least two thermal diodes further includes adjusting one or more of: (1) a geometry of the at least two thermal diodes; (2) a thermal effusivity of the at least two thermal diodes; (3) a temperature oscillation frequency associated with the at least two thermal diodes; or (4) a spatial and temporal gradient associated with the at least two thermal diodes. 
     
     
       20. The method of  claim 1 , further comprising operating the thermal resonance device having at least two thermal diodes to use a first thermal mass associated with a first of the at least two thermal diodes and a second thermal mass associated with a second of the at least two thermal diodes to capture ambient thermal fluctuations, the first and second thermal masses being different objects. 
     
     
       21. The method of  claim 20 , wherein the first and second thermal masses have a primary purpose that does not include capturing ambient thermal fluctuations. 
     
     
       22. The method of  claim 13 , further comprising operating the thermal resonance device having at least two thermal diodes to use a first thermal mass associated with a first of the at least two thermal diodes and a second thermal mass associated with a second of the at least two thermal diodes to capture ambient thermal fluctuations, the first and second thermal masses being different objects. 
     
     
       23. The method of  claim 22 , wherein the first and second thermal masses have a primary purpose that does not include capturing ambient thermal fluctuations.